Many people desire a longer operating lifetime for their battery-powered electronic, such as mobile telephones, MP3 players, and so forth. Typically in order for these battery-powered devices to conserve electrical power, their current consumption is managed preferably retaining operating characteristics thereof unaltered over as much of the battery operating range as possible.
Numerous techniques and publications exist, which detail methods and apparatus for improving power amplifier (PA) power consumption by varying supply voltage provided thereto using a DC to DC converter. For example, U.S. Pat. No. 6,624,702, discloses circuitry for controlling of a DC to DC converter in dependence upon sensed RF output signal power for the PA, which enables operation of the PA at high efficiencies as RF output signal power is changed.
Other variants use an envelope tracking power supply coupled with collector terminals of bipolar transistors in combination with a variable base terminal supply current in order to monitor PA power consumption. Unfortunately, envelope tracking requires a complex power supply and has yet to be demonstrated in a practical fashion.
For example, U.S. Pat. Nos. 6,630,867 and 6,646,511 disclose the use of a power management unit in conjunction with a PA in order to monitor the power consumption of the PA and to vary an operating voltage applied to the PA in dependence upon the power consumption.
Unfortunately, the standard approach in using a DC to DC converter requires very large regulator components capable of delivering an output signal current of over 700 mA with a clean output spectrum. In general, the size and conversion efficiency of this regulator type is more problematic at high current due to dropping losses in pass transistors. Thus, using prior art DC to DC converter technology result in high cost and size issues. Additionally, the challenge in using the prior art circuits arises when these circuits are used in current sensitive devices, such as portable electronic devices.
A need therefore exists to provide a power amplifier with improved power consumption efficiency. It is therefore an object of the invention to provide a power amplifier (PA) that utilizes a low current DC to DC converter for operation thereof.